Posted June 21, 2023

IAPMO Water Demand Calculator Version 2.2 Available for Download

Upgraded algorithm is faster and more accurately predicts peak indoor water demand.

The International Association of Plumbing and Mechanical Officials (IAPMO®) is excited to announce that the Water Demand Calculator™ version 2.2 is now available for download.

While the basic template of version 2.1 of the calculator remains intact, version 2.2 includes several new features. First, version 2.2 implements a new algorithm called the method of convolution to replace exhaustive enumeration. The new algorithm is faster and has a smoother transition to the other methods of computation. This new computation method assures accurate predictions of peak indoor water demand.

A second new feature of the Water Demand Calculator version 2.2 is the enhanced display showing the method of computation. After running the Water Demand Calculator, a new box in the computed results column shows the exact algorithm used in the calculation.

A third new feature of version 2.2 is that the results of the peak flow calculation are now downloaded in a Microsoft Excel spreadsheet rather than a text file. The spreadsheet displays all the results and the list of fixtures and fixture counts entered into the calculation. An updated user guide is also available for version 2.2.

“The Water Demand Calculator has become more robust while remaining fast, accurate and user-friendly,” said Dan Cole, IAPMO’s senior director of Technical Services. “Increasing the accuracy in predicting peak water demand for single- and multifamily dwellings will lead to reductions in pipe sizing accompanied by additional cost savings.”

The Water Demand Calculator version 2.2 and user guide may be downloaded at